* Two private polls show "Yes" vote wins referendum
* Opponents fear president amassing excessive power (Adds analysis, context, poll details)
By Eduardo Garcia and Alexandra Valencia
QUITO, May 7 (Reuters) - Ecuador's President Rafael Correa hailed victory on Saturday after two polls showed him winning a referendum on judicial and media reforms that opponents say are a power grab threatening the Andean nation's democracy.
"We've won by more than 20 points," said Correa. "The Ecuadorean people have triumphed, the truth has triumphed."
If confirmed by the election authority, the result would strengthen the popular but domineering Correa's political standing in the South American OPEC member and put him in a strong position for a re-election bid in 2013.
A private tracking poll by Cedatos-Gallop showed an average of 57 percent of voters backing all 10 questions on a referendum that was essentially a vote of confidence on the flamboyant Correa, 48, who has governed since 2007.
An exit poll by Santiago Perez Investigacion y Estudios showed more than 60 percent said "Yes" to all questions.
"We're really happy!" Foreign Minister Ricardo Patino told Reuters. Official results were due later on Saturday.
Full coverage of Ecuador's referendum [ID:nECUADOR]
Q+A-What is the referendum about? [ID:nN137741]
Political risks in Ecuador [ID:nRISKEC]
Factbox on Ecuador and Correa [ID:nN27176839]
Correa has maintained high popularity among the poor and lower-middle classes thanks to big spending on schools, roads and hospitals. Rivals accuse him of an autocratic streak akin to his ally Hugo Chavez, the president of Venezuela, and fear he could use the reforms to persecute opponents.
"We're giving Correa too much power, but it doesn't matter. Someone has to tidy up this mess," said "Yes" voter Cesar Acosta, 67, echoing Correa's original justification for the vote to root out graft and inefficiency in courts.
The most controversial two proposals set the foundations for a new justice system in which Correa will have more direct say over appointments. He argues that corrupt judges have to go so police can better fight crime, a huge concern for the South American nation's 14 million people.
"Correa will have the ability to restructure the court system and essentially hand-pick judges ... (which) will further concentrate power in the executive and limit checks," political risk consulting firm Eurasia Group said.
Other reforms include more controls on media, with whom Correa has been dueling regularly, and a ban on bullfights.
As he voted, Correa -- the strongest leader in decades in a country notorious for political instability -- bristled at claims he was taking Ecuador down an autocratic route.
"They've been saying it's totalitarian ... (a word) used for a state in which things are done by force. We're doing this democratically," he said.
Ecuadoreans seemed to have voted en masse, especially since those who did not vote face a fine of about $25. Local TV showed voters walking through muddy roads in the Amazon area, wearing indigenous outfits in an Andean province and lining up in front of polling stations in the Galapagos Islands.
Opposition leaders say Correa is amassing too much power. "I think he's tired of the constitution," former presidential aide turned critic Alberto Acosta told Reuters.
The charismatic and voluble Correa forms part of a regional alliance of leftist Latin American presidents that includes Chavez in Venezuela and Evo Morales in Bolivia.
They are fervent critics of U.S. "imperialism" and have sought to boost state revenues from their country's energy resources to spend on social projects.
RETHINK FOR RIVALS
If their defeat is confirmed in the referendum, Correa's bruised rivals may be forced to rethink their strategy and possibly rally behind a united leader ahead of 2013.
Correa is likely to feel emboldened, but his victory will also fuel criticism he wants to install communist-style rule in Ecuador, and that could cost him support among educated voters in Quito and Guayaquil, Ecuador's biggest urban areas.
Victory should allow Correa to rein in dissent in the ruling Alianza Pais movement, which could help his chances of getting legislation approved.
Analysts do not expect Correa to change his policies toward oil and mining investors after such a sweeping victory.
"In the oil sector, the government has already extracted significant benefits under its new contracts. ... (It) will offer mining companies relatively generous terms in its initial contracts in order to attract foreign investment to help develop the nascent mining sector," Eurasia Group said.
Correa's tough stance toward the media has fueled fears that two reforms aimed at limiting media ownership and holding journalists "responsible" for their stories will let him silence criticism of his policies. (Additional reporting by Jose Llangari and Santiago Silva; Editing by Andrew Cawthorne, Peter Cooney and Todd Eastham)